Various types of the abovementioned self-standing manually operated elevating screens have been proposed. For example, a system has been used in which the screen is held in a deployed position by pivot-connecting the upper end of a pantograph type linking mechanism to the approximate center of the upper-end supporting member of the screen with respect the transverse direction of the screen).
However, in cases where the upper end of a linking mechanism is pivot-connected only to the approximate center of the upper-end supporting member of the screen with respect to the transverse direction of the screen as described above, the left-right balance adjustment and the like must be performed with high precision in order to accomplish the smooth extension and retraction of the linking mechanism with good stability, and in order to cause the screen to stand by itself with good stability. Furthermore, smooth raising and lowering of the screen cannot be accomplished unless the raising and lowering of the screen is effected via the center of the upper-end supporting member with respect to the transverse direction, so that there may be a drop in operability.
For example, a screen which is constructed so that the left and right ends of an upper-end supporting member and the left and right ends of a supporting frame are connected and supported by means of left and right linking mechanisms consisting of upper-end side arms and supporting-frame side arms, thus making it possible to accomplish the smooth extension and retraction of the linking mechanisms with good stability, and to cause the screen to stand by itself with good stability, has already been proposed as a screen which solves the abovementioned problems (for example, see FIG. 1 of Japanese Patent No. 3243037.
However, the abovementioned screen disclosed in Japanese Patent No. 3243037 (See FIG. 1 of Japanese Patent No 3243037) has a construction in which the left and right linking mechanisms can be freely extended and retracted independently of each other, and has a construction in which the left and right linking mechanisms are caused to move in linkage with one end [of each linking mechanism] connected to the upper-end supporting member. Accordingly, if the screen is pushed downward by way of the left or right end portion of the upper-end supporting member of the screen in a deployed state, the upper-end supporting member will first drop considerably on the side that is pushed, thus causing this member to assume an inclined attitude, so that the linking mechanism on the side that has dropped is greatly shortened. As a result, a large load is applied only to the linking mechanism on the shortened side, and this may lead to deformation or damage of the linking mechanism.
With the foregoing in view, it is an object of the present invention to provide a self-standing manually operated elevating screen which makes it possible to raise and lower the screen over a long period of time without the occurrence of any trouble such as deformation, damage or the like, and which makes it possible to simplify the construction that is used for this purpose.